I was reading Matthew Henry’s commentary on Mt 13:10-17 and saw this nugget.
A parable is a shell that keeps good fruit _for_ the diligent, but keeps it _from_ the slothful.
To some extent, Christ taught the crowds in parables to make the truth _harder_ , not easier, to get at – in order to “weed out” casual observers. But for those who were enlightened by the Holy Spirit, and willing to work at it (see Proverbs 2:3-5), these parables contain profound truth. And they are presented in such a way that they stick with you. It’s far easier to remember the parable of the prodigal son than it is to memorize Romans 12:1-2, for instance.